Lightweight wall repair compounds

ABSTRACT

Herein are disclosed wall repair compounds comprising at least one or more polymeric binder latex emulsions, one or more inorganic fillers, and comprising an amount of organic polymeric thickener that is less than about 0.1 percent by weight based on the total weight of the wall repair compound. In certain embodiments, the wall repair compound comprises an inorganic filler system selected such that such that synthetic inorganic fillers comprise essentially 100 percent of the inorganic filler used. In certain embodiments, the wall repair compound comprises one or more glycol ether smoothing agents.

BACKGROUND

Interior walls of buildings are often constructed using gypsum wallboardpanels (sometimes referred to as drywall). Where cavities, recesses,holes, etc., may be present (due to imperfections or damage) it iscommon to use wall repair compound (often referred to as “spackling”) tofill such cavities. Conventional wall repair compounds often include oneor more inorganic fillers, one or more polymeric resin binders, andvarious thickeners and other additives. In particular, lightweight wallrepair compounds have been developed which often contain, among otherinorganic fillers, relatively low density fillers such as glass bubbles,hollow silica, or expanded perlite.

Wall repair compounds often comprise a significant amount of water(e.g., greater than about 20 percent by weight); such that, after thewall repair compound is applied to a wall, the water evaporates over aperiod of time resulting in the formation of a dried, hardened materialwhich can be sanded, painted, etc.

SUMMARY

Herein are disclosed lightweight wall repair compounds comprising atleast one or more polymeric binder latex emulsions and inorganicfillers; and, comprising an amount of organic polymeric thickener thatis less than about 0.1 percent, by weight, of the as-formulated wallrepair compound.

In various embodiments, the lightweight wall repair compounds disclosedherein comprise an inorganic filler system selected such that such thatsynthetic inorganic fillers (as defined herein) comprise at least 95,99, or essentially 100 percent, by weight, of the inorganic filler inthe wall repair compound. An advantage of at least some of theseembodiments is that synthetic inorganic fillers may be viewed (e.g., byend users) as preferable to natural inorganic mineral fillers.

In certain embodiments, the lightweight wall repair compounds disclosedherein comprise one or more smoothing agents that have been found toadvantageously effect the consistency of the compound such that it canbe easily applied (for example, such that it is easily spreadable yetdoes not run, sag or slump once applied, e.g. to a vertical wall). Suchsmoothing agents (described in further detail herein) comprisehydrocarbon molecules comprising exactly one hydroxyl group and furthercomprising exactly one or exactly two ether groups, and often referredto as glycol ethers. The inventors have found that such glycol ethersmoothing agents can be added at low amounts (e.g., from about 0.025 toabout 2.5 percent, by weight) with advantageous, and unexpected,technical effects.

The inventors have found that at least certain of the compositionsdisclosed herein can advantageously result in very low shrinkage upondrying of the applied compound, which can enable the compound to drywithout cracking, deforming, etc. A further advantage of at leastcertain embodiments disclosed herein is the ability of the wall repaircompound to survive freeze-thaw cycles in usable form without thenecessity of adding components such as anti-freeze compounds. Anadditional advantage of at least certain embodiments disclosed herein isthat, in the event that the wall repair compound has been accidentallyallowed to lose a small amount of water by evaporation (e.g., by the lidof the storage container being incompletely sealed) the compound may beable to be reconstituted substantially into its original form by way ofstirring a small amount of water into the compound.

Thus in one aspect, herein is disclosed a wall repair compound,comprising: from about 20 percent to about 80 percent by weight aqueouslatex binder emulsion; from about 20 percent to about 70 percent byweight of an inorganic filler system, wherein the inorganic fillersystem is comprised of essentially 100 percent by weight syntheticinorganic filler; from about 0.025 percent to about 2.5 percent byweight of at least one glycol ether smoothing agent that comprisesexactly one hydroxyl group and exactly one or exactly two ether groups;and, less than about 0.1 percent by weight of organic polymericthickener.

In another aspect, herein is disclosed a wall repair compound comprisingfrom about 20 percent to about 70 percent by weight of an inorganicfiller system, wherein the synthetic inorganic filler comprisessubstantially spherical synthetic particles and wherein the particlescomprise a set of relatively large diameter glass bubbles and a set ofrelatively small ceramic microspheres, with the ratio of the medianparticle size of the glass bubbles to the median particle size of theceramic microspheres being in the range of about 5:1 to about 40:1.

These and other aspects of the invention will be apparent from thedetailed description below. In no event, however, should the abovesummaries be construed as limitations on the claimed subject matter,which subject matter is defined solely by the attached claims, as may beamended during prosecution.

Although terms such as “first” and “second”, and “large” and “small”,may be used in this disclosure, it should be understood that those termsare used in their relative sense only.

DETAILED DESCRIPTION

Herein are disclosed compounds suitable for filling and repairingcavities, cracks, holes, or other imperfections in a wall surface (suchas a gypsum wallboard surface). Such compounds comprise at least one ormore polymeric binder latex emulsions and one or more inorganic fillersand further comprise an amount of organic polymeric thickener that isless than about 0.1 percent, by weight, based on the total weight of thewall repair compound as formulated.

The wall repair compound disclosed herein comprises an inorganic fillersystem that comprises one or more inorganic fillers. In variousembodiments, the inorganic filler system comprises at least about 20,30, or 40 percent, by weight, of the wall repair compound (this and allother percentages by weight disclosed herein are based on the totalas-formulated weight of the wall repair compound (i.e., includingwater), unless otherwise noted). In further embodiments, the inorganicfiller system comprises at most about 70, 60 or 50 percent, by weight,of the weight of the wall repair compound as formulated.

Inorganic fillers are often naturally occurring minerals which are minedfrom the earth. In this context, a natural inorganic filler is thusdefined herein as a mineral that has been extracted from the earth inits naturally occurring form, and, while possibly being subjected topurification and/or modification processes such as filtering, screening,degritting, bleaching, beneficiation, centrifugation, etc., is usedwhile still substantially in its naturally occurring form (althoughpossibly in a more purified or concentrated form). Such naturalinorganic fillers often comprise substantially crystalline structures,and are often comprised substantially of particles that aresubstantially non-spherical and/or that comprise somewhat irregular ornonuniform, or very irregular or nonuniform, shapes. In this context, amineral which has been calcined by exposure to a temperature sufficientto drive off waters of hydration (but not sufficient to cause melting ofthe material or to cause a change in the structure of the material fromcrystalline to amorphous), is still considered to be a natural inorganicfiller. In this context, the term inorganic fillers includes suchfillers as have been modified to include organic surface groups,coatings, etc.

Natural inorganic fillers can include for example calcite, witherite,rutile, anatase, ilmenite, mica, sericite, perlite, talc, limestone,silica, barite, gypsum, calcined gypsum, kaolinite, montmorillonite,attapulgite, illite, saponite, hectorite, beidellite, stevensite,sepiolite, bentonite, pyrophyllite, diatomaceous earth, and the like.

In certain embodiments, the inorganic filler systems used herein arecomprised of at least 95 percent, at least 99 percent, or essentially100 percent, by weight, of synthetic inorganic filler. In this context,essentially 100 percent by weight synthetic inorganic filler means thatall of the inorganic filler chosen to be used in the formulation of thewall repair compound is synthetic, such that only such (possiblyundetectable) trace amounts of naturally occurring mined mineral fillersare present as may be known to one of skill in the art as being inherentor unavoidable in the standard production processes of such syntheticinorganic fillers.

The term synthetic inorganic filler includes any filler that has beentransformed, regenerated, recrystallized, reconstituted, etc. from anoriginal state (which may be its naturally occurring, mined state) intoits current state by a chemical synthesis process (e.g., precipitatedfrom solution, generated by flame hydrolysis, etc.) or by a physicalsynthesis process (e.g., precipitated from a gaseous phase, solidifiedby way of a sol-gel process, etc.). The designation synthetic inorganicfiller also includes any filler that has been substantially transformedfrom an original state (which may be its naturally occurring, minedstate) into its current state by a physical synthesis process of beingbrought into an at least partially softened or molten state and thensolidified by cooling, such that any substantially crystalline structurethat may have existed in the natural state is substantially erased suchthat the material is now in a substantially amorphous form (e.g.,comprising less than about 0.5 percent crystallinity by weight). Suchprocesses may include for example melt processing, flame-fusion, and thelike.

In this context, synthetic inorganic fillers include for exampleso-called glass bubbles (such as those available from 3M Company of St.Paul, Minn., under the trade designation 3M Glass Bubbles), ceramicmicrospheres (such as those available from 3M Company under the tradedesignation 3M Ceramic Microspheres), synthetic clays (e.g., syntheticsilicate clays such as those available under the trade designationLaponite from Southern Clay Products, Gonzales, Tex., precipitatedsilica, fumed silica, vitreous silica, synthetic titanium dioxide (asmade, for example, by the sulfate process or the chloride process),synthetic (precipitated) calcium carbonate (as made, for example, bypassing carbon dioxide through a solution of calcium hydroxide), and thelike.

In this context, the term synthetic inorganic fillers includes suchsynthetic inorganic fillers as have been modified to include organicsurface groups, coatings, etc.

In various embodiments, the synthetic inorganic filler comprises lessthan 0.5, 0.1, or 0.05 percent crystalline material, by weight, when abulk sample of the filler is tested by X-Ray Diffraction methods.

In certain embodiments the synthetic inorganic filler used hereincomprises a bimodal particle size mixture of larger synthetic inorganicfiller particles and smaller synthetic inorganic filler particles. Invarious specific embodiments, the synthetic inorganic filler used hereincomprises a bimodal particle size mixture of synthetic inorganic fillerparticles comprising a particle size ratio of larger particle sizefiller to smaller particle size filler (as obtained by ratioing themedian particle size of the two filler populations) of at least about5:1, 10:1 or 15:1. In various specific embodiments, the particle sizeratio is at most about 40:1, 30:1, or 20:1.

In various embodiments, the larger particle size synthetic inorganicfiller particles comprise a median particle size of at least about 15,30 or 40 microns, and of at most about 80, 65 or 55 microns. In variousembodiments, the smaller particle size synthetic inorganic fillerparticles comprise a median particle size of at least about 1, 2, or 3microns, and of at most about 15, 10 or 5 microns.

In a particular embodiment, such synthetic inorganic fillers arecomprised of substantially spherical particles. In this context,substantially spherical denotes that a substantial majority of theparticles are spherical except for such occasional deviations,deformities, etc. as are known to those of skill in the art to beoccasionally encountered in the manufacturing processes used to producethe particles (for example, somewhat misshapen particles may beoccasionally produced, two or more particles may agglomerate or adhereto each other, and so on).

Suitable substantially spherical synthetic inorganic fillers as definedherein include so-called glass bubbles (such as those available from 3MCompany of St. Paul, Minn., under the trade designation 3M GlassBubbles), and ceramic microspheres (such as those available from 3MCompany under the trade designation 3M Ceramic Microspheres). Such glassbubbles can be synthesized, for example, by a process as described inU.S. Pat. Nos. 3,365,315 and 4,391,646. Such ceramic microspheres can besynthesized, for example, by sol-gel processes, as described for examplein U.S. Pat. Nos. 3,709,706 and 4,166,147. Other methods potentiallyuseful for making ceramic particles and/or microspheres are describedin, for example, U.S. Pat. No. 6,027,799.

In the certain embodiments the synthetic inorganic filler used hereincomprises a bimodal particle size mixture of larger substantiallyspherical synthetic inorganic filler particles and smaller substantiallyspherical synthetic inorganic filler particles. In various specificembodiments, the synthetic inorganic filler used herein comprises abimodal particle size mixture of substantially spherical syntheticinorganic filler particles comprising a particle size ratio ofsubstantially spherical larger particle size filler to substantiallyspherical smaller particle size filler (as obtained by ratioing themedian particle size of the two filler populations) of at least about5:1, 10:1 or 15:1. In various specific embodiments, the particle sizeratio is at most about 40:1, 30:1, or 20:1.

In particular embodiments, the larger particle size synthetic inorganicfiller comprises glass bubbles and the smaller particle size syntheticinorganic filler comprises ceramic microspheres. In various embodiments,the glass bubbles comprise a median particle size of at least about 15,30 or 40 microns, and of at most about 80, 65 or 55 microns. In variousembodiments, the ceramic microspheres comprise a median particle size ofat least about 1, 2, or 3 microns, and of at most about 15, 10 or 5microns.

In such compounds, the glass bubbles generally comprise a true densitythat is less than that of the ceramic microspheres. Thus in variousembodiments, the ceramic microspheres comprise a true density of atleast about 2.0 or 2.2 g/cc, and of at most about 2.6 or 2.4 g/cc. Invarious embodiments, the glass bubbles comprise a true density of atleast about 0.1, 0.15, or 0.2 g/cc, and of at most about 0.6, 0.4, or0.3 g/cc.

In such compounds, the glass bubbles are generally present at an amountthat is equal to or higher than the amount of ceramic microspheres. Thusin various embodiments, the glass bubbles and the ceramic microspheresare present at a weight ratio of at least about 1:1 glassbubbles/ceramic microspheres, or at least about 1.5:1 glassbubbles/ceramic microspheres. In various embodiments, the glass bubblesand the ceramic microspheres are present at a weight ratio of at mostabout 3:1 glass bubbles/ceramic microspheres, or at most about 2:1 glassbubbles/ceramic microspheres.

The inventors have observed that the use of such substantially sphericalfillers as described above, and in particular the use of a bimodalmixture of such fillers, can help provide a wall repair compound thatspreads extremely easily and yet does not sag, run or slump to anexcessive degree when applied to a vertical wall.

The wall repair compound disclosed herein comprises at least onepolymeric resin binder. Such binders are often supplied as an aqueouslatex emulsion (for example comprising between 40-60 percent solids ofpolymeric resin binder, in water). Polymeric resins potentially suitablefor binders in the present application include for example thewell-known acrylic polymers and copolymers, polyvinyl acetate polymersand copolymers, ethylene vinyl acetate polymers and copolymers,styrene-butadiene polymers and copolymers, polyacrylamide polymers andcopolymers, natural rubber latex, natural and synthetic starch, casein,and the like. Such binders can be used alone or in combination with oneanother.

In various embodiments, the binder latex emulsion can comprise at leastabout 20, 30, or 40 percent, by weight, of the wall repair compound. Infurther embodiments, the binder latex emulsion can comprise at mostabout 80, 70 or 60 percent, by weight, of the wall repair compound.

In a specific embodiment, the polymeric resin binder comprises a vinylacrylic polymer, copolymer or blend. Such materials can comprise any ofa wide variety of polymers and/or copolymers made for example by thepolymerization of ethylenically unsaturated monomers that compriseacrylate and/or methacrylate groups. Such vinyl acrylic polymeric binderresins are widely known in, for example, the paint industry. Othermonomers, polymers, additives, etc. may also be present for a variety ofpurposes. Such vinyl acrylic binders have the particular advantage thatmany common paints contain similar binders, thus the dried wall repaircompound may not need to be primed to avoid such common problems asflashing or reverse flashing, upon painting of the wall containing thedried wall repair compound.

In various embodiments, the polymeric resin binder comprises a glasstransition temperature (T_(g)) of around room temperature (e.g., fromabout 15° C. to about 35° C.; or, from about 20° C. to about 30° C.).The term “glass transition temperature” is of course a term well knownin the art and generally relates to a softening temperature indicativeof the onset of long range translational motion of polymer molecules. AT_(g) in the above-described temperature range may render the binderwell suited for fusing and coalescing under ambient conditions after thewall repair compound has been applied and allowed to dry. Also, a T_(g)that is excessively higher than room temperature might bedisadvantageous in that in the dried compound the binder might be belowits T_(g) thus in a relatively brittle state thus rendering the driedcompound excessively susceptible to cracking. Conversely, a T_(g) thatis excessively lower than room temperature might be disadvantageous inthat the dried wall repair compound might be so soft or rubbery as tomake it difficult to perform operations such as sanding. It may also beadvantageous for the binder to have a relatively broad T_(g) (e.g.,exhibiting a somewhat broad T_(g) peak covering an interval of at leastabout 5 or 10° C.) such that the binder does not exhibit a relativelysharp change in physical properties upon changes in ambient temperature.

In a particular embodiment, the latex binder emulsion comprises theacrylic binder latex emulsion available (as a 50 percent solids latexemulsion) from Dow Chemical of Midland, Mich., under the tradedesignation UCAR 626.

Conventional wall repair compounds often comprise organic polymericthickeners. Such organic polymeric thickeners are often used, forexample to provide an increased viscosity of the wall repair compoundsuch that the compound does not excessively sag, slump or run (e.g.,when applied to a vertical wall). Such organic polymeric thickeners areoften designed to exhibit their thickening effect by their interactionwith the water that is present in the wall repair compound. Thus,commonly used organic polymeric thickeners are often water soluble orwater swellable (e.g., at around 22° C.). (Such materials may beoccasionally referred to in the art as gelling agents, bodying agents,water retention agents, etc.). Often, such materials are polyhydroxycompounds that have at least two, and often ten, twenty, or more,hydroxyl groups.

Such organic polymeric thickeners can be synthetic, can be naturalproducts, and/or can be obtained or derived from natural products. Suchthickeners can include for example polysaccharides and derivativesthereof, for example the well known cellulose ethers (e.g., methylcellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose,hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxyethylhydroxypropyl cellulose, ethylhydroxyethyl cellulose, and sodiumcarboxymethyl cellulose). Such thickeners can also include for examplepolyethylene glycol, polyethylene oxide (and/or polyethyleneoxide/polypropylene oxide copolymers), polyvinyl alcohol, polymers orcopolymers of ethylenically unsaturated carboxylic acids and theirderivatives, such as acrylic acid and acrylamide, guar gum, xanthan gum,alginates, tragacanth gum, pectin, amylopectin, dextran, polydextrose,and the like.

Such organic polymeric thickeners often comprise a relatively highmolecular weight, e.g. greater than 500 g/mole, or greater than 5000g/mole or higher.

Such organic polymeric thickeners can also be recognized by those ofordinary skill in the art by, for example, their ability to increase,often substantially increase, the viscosity of water upon their additionto water.

The inventors have found that it in certain embodiments it isadvantageous to maintain the concentration of such organic polymericthickeners below a predetermined amount (of the wall repair compound asformulated). This has been observed by the inventors to appear to beable to help achieve a desirably low shrinkage of the compound upondrying. The discoveries disclosed herein thus enable the formulation oflow-shrink wall repair compounds that also comprise unexpectedlyadvantageous resistance to sagging, running or slumping, even at suchlow levels (or in the absence) of thickener. Thus, in variousembodiments, the wall repair compounds disclosed herein comprise lessthan 0.1, 0.05, or 0.02 percent, by weight, organic polymeric thickener.In such small quantities, such organic polymeric thickeners may serveprimarily only as a processing aid (for example, to help in dispersingthe inorganic filler(s) in the aqueous mixture) rather than servingtheir conventional purpose in the art, which is to thicken the compoundso it does not run, sag or slump when applied to a vertical wall.

In a particular embodiment, the inventors have found that themaintaining of a level of organic polymeric thickener of less than 0.1,0.05, or 0.02 percent by weight, may be employed in a wall repaircompound comprising the above-described bimodal mixture of substantiallyspherical synthetic inorganic fillers, to result in a compound with aparticularly advantageous combination of smoothness, ease of spreading,and resistance to shrinkage upon drying.

The inventors note that certain natural or synthetic inorganic fillers(for example, clays such as attapulgite, bentonite, montmorillonite,illite, kaolinite, sepiolite, the synthetic clay available under thetrade designation Laponite from Southern Clay Products, etc.), while notnecessarily water soluble, are known to exhibit a thickening (e.g.,viscosity-increasing) effect when dispersed in water. Such materials(particularly those that absorb water and/or swell upon exposure towater) have commonly been used as thickeners in wall repair compounds(they are also occasionally referred to in the art as rheologymodifiers, non-leveling agents, etc.), and are known in the art tocontribute to shrinkage upon drying (as discussed, for example, in U.S.Pat. No. 4,824,879). Thus, in certain embodiments, the wall repaircompounds disclosed herein comprise less than 0.1, 0.05, or 0.02percent, by weight, of (natural or synthetic) inorganic thickeningfiller clay. In a particular embodiment, the wall repair compoundsdisclosed herein comprise less than about 0.1 percent by weight ofinorganic thickening filler clay and further comprise less than about0.1 percent by weight of organic polymeric thickener.

In certain embodiments, the lightweight wall repair compounds disclosedherein comprise one or more smoothing agents which have been found toadvantageously affect the consistency of the compound. Specifically, theinventors have found such smoothing agents to impart a smoothconsistency to the compound (absent the smoothing agent the compound maytake on a more crumbly appearance) such that the compound is more easilyspreadable yet does not run, sag, slump or crumble, once applied, e.g.to a vertical wall. In contrast to the above-described thickeners, suchsmoothing agents appear to function to reduce the apparent viscosity ofthe wall repair compound rather than to increase it (while, again, notcausing unacceptable sagging or slumping).

The presence of such a smoothing agent has also been found by theinventors to improve the ability of the compound to be brought back tothe above-described smooth consistency by the addition of a small amountof water, in the event that the compound is inadvertently allowed tolose water (e.g., by the container being left open for a period oftime). In the absence of such a smoothing agent, the inventors havefound that the addition of water may only serve to reduce the viscosityof the compound such that unacceptable sagging or slumping results.

In a particular embodiment, the inventors have found that such smoothingagents may be employed in a wall repair compound comprising theabove-described bimodal mixture of substantially spherical syntheticinorganic fillers, to result in a compound with a particularlyadvantageous combination of smoothness, ease of spreading, andresistance to running, slumping, or sagging.

In a further particular embodiment, the inventors have found that suchsmoothing agents may be employed in a wall repair compound comprisingthe above-described bimodal mixture of substantially spherical syntheticinorganic fillers, and comprising a level of organic polymeric thickenerof less than 0.1, 0.05, or 0.02 percent by weight, to result in acompound with a particularly advantageous combination of smoothness,ease of spreading, resistance to shrink upon drying, and resistance torunning, slumping, or sagging.

Such viscosity-reducing smoothing agents comprise hydrocarbon moleculescomprising exactly one hydroxyl group and further comprising an etherlinkage. In one embodiment, the smoothing agent comprises one or more ofthe compounds generally known in the art as glycol ethers and comprisinga linear hydrocarbon chain with exactly one or exactly two ether groupsin the chain, and bearing a single hydroxyl group. The hydroxyl groupmay for example be attached to a terminal carbon of the chain, orattached to a carbon adjacent to a terminal carbon of the chain, orattached to some other carbon of the molecule. The linear chain may alsocomprise one or more methyl groups or other alkyl groups attached to thecarbons of the chain.

Such glycol ether smoothing agents typically comprise a relatively lowmolecular weight (e.g., from about 90 g/mole to about 250 g/mole); aretypically liquid at room temperature (e.g., 22° C.); and, whiletypically being partially or completely miscible with water, do not actto substantially increase the viscosity of water when added to water.

As such, these glycol ether smoothing agents are distinguished fromorganic polymeric thickeners such as the above-described relatively highmolecular weight polyhydroxy materials that comprise multiple hydroxylgroups. As such, they are also distinguished from organic polymericthickeners such as poly(ethylene oxide) and/or polyethylene glycol andderivatives thereof, which, although possibly not possessing hydroxyls,possess multiple (e.g., greater than three) ether linkages which renderthe molecules relatively hydrophilic and serve to make them function ina well known capacity as aqueous viscosity-increasing agents.

Thus in summary, the glycol ether smoothing agents disclosed herein maybe distinguished from conventional thickeners based on their chemicalformula and/or their chemical structure; and/or, when used in a wallrepair compound, by the apparent viscosity-lowering effect of thesmoothing agents, and/or by the absence of the relatively high shrinkupon drying which is often associated with conventional thickeners.

The glycol ether smoothing agents disclosed herein may also bedistinguished from relatively small, low molecular weight (e.g., lessthan about 500 g/mole) molecules that have multiple hydroxyls. Such lowmolecular weight polyhydroxy molecules have been found by the inventorsnot to have the advantageous effects of the glycol ether smoothingagents. For example, a wall repair formulation comprising glycerol (MWof 92 g/mole, with three hydroxyls) was found by the inventors toexhibit a much tackier consistency which lacked certain advantageousproperties of the compositions described above. Such low molecularweight polyhydroxy molecules are sometimes found in wall repaircompounds (for example, as mentioned in U.S. Pat. No. 4,629,751 as beinguseable to inhibit gelation of certain wall repair compositions). Thus,in certain embodiments, the wall repair compounds disclosed hereincomprise less than 0.1, 0.05, or 0.02 percent, by weight, of lowmolecular weight polyhydroxy molecules.

Thus in summary, the inventors postulate, without wishing to be limitedby theory or mechanism, that materials such as polyhydroxy thickeners,polyether thickeners (such as polyethylene glycol and polyethyleneoxide), and even polyhydroxy small molecules (such as glycerol), may, byvirtue of their sufficiently high number of hydrophilic groups such ashydroxyls and/or ether groups, interact with water in the wall repaircompound, and/or with the surface of inorganic fillers in the compound,at least to increase the viscosity of the system, and possibly to formquasi-network structures. In contrast, glycol ether smoothing agents asdescribed herein may not be as capable of forming such networkstructures (which may account for their failure to cause a substantiallyincreased viscosity), and in addition appear to be able to undergo someother kind of interaction which results in the advantageous effects(e.g., apparent lowering of viscosity, increased spreadability withoutincurring excessive sag or slump, etc.) that have been documented hereinby the inventors.

The inventors note that glycol ethers have found use in the latex paintand coatings industries, where their use is often described by those ofskill in the art as facilitating the coalescence of the polymeric resinbinder when the latex is dried. In the present use, in contrast, themost obvious advantageous effect of such smoothing agents appears to bethe providing of a smooth consistency of the as-formulated compoundrather than any obvious effect that occurs upon drying of the compound.Possibly associated with this is the fact that the inventors have foundthe beneficial effects of such smoothing agents to occur at levelssomewhat far below the typical use of, for example, glycol ethers in thepaint arts (as related, for example, in U.S. Pat. No. 4,283,320).

Thus, in various embodiments, the wall repair compounds described hereincomprise one or more glycol ether smoothing agents that are present intotal in an amount of at most about 2.5 percent, at most about 1.5percent, or at most about 0.5 percent, by weight (of the total wallrepair compound as formulated). In various additional embodiments, theone or more glycol ether smoothing agents are present in total in anamount of at least about 0.025 percent, at least about 0.05 percent, orat least about 0.15 percent, by weight.

Suitable glycol ether smoothing agents may be chosen for example fromthose glycol ethers available from Dow Chemical under the tradedesignation Dowanol, or those available from Dow Chemical under thetrade designation Cellosolve.

In one embodiment, smoothing agents are chosen from glycol ethers thatcomprise exactly one hydroxyl group and exactly one ether group. Thisgroup includes, for example, propylene glycol butyl ether (availablefrom Dow Chemical under the trade designation DOWANOL PnB), propyleneglycol methyl ether (available from Dow Chemical under the tradedesignation DOWANOL PM), propylene glycol propyl ether (available fromDow Chemical under the trade designation DOWANOL PnP), propylene glycolphenyl ether (available from Dow Chemical under the trade designationDOWANOL PPh), ethylene glycol butyl ether (available from Dow Chemicalunder the trade designation Butyl CELLOSOLVE), ethylene glycol propylether (available from Dow Chemical under the trade designation PropylCELLOSOLVE), ethylene glycol hexyl ether (available from Dow Chemicalunder the trade designation Hexyl CELLOSOLVE), ethylene glycol phenylether (available from Dow Chemical under the trade designation DOWANOLEph), and mixtures thereof.

In another embodiment, smoothing agents are chosen from glycol ethersthat comprise exactly one hydroxyl group and exactly two ether groups.This group includes, for example, dipropylene glycol butyl ether(available from Dow Chemical under the trade designation DOWANOL DPnB),dipropylene glycol methyl ether (available from Dow Chemical under thetrade designation DOWANOL DPM), dipropylene glycol propyl ether(available from Dow Chemical under the trade designation DOWANOL DPnP),diethylene glycol butyl ether (available from Dow Chemical under thetrade designation Butyl CARBITOL), diethylene glycol methyl ether(available from Dow Chemical under the trade designation MethylCARBITOL), diethylene glycol hexyl ether (available from Dow Chemicalunder the trade designation Hexyl CARBITOL), diethylene glycol ethylether (available from Dow Chemical under the trade designationCARBITOL), mixtures thereof, and/or mixtures with the above-listedglycol ethers that comprise exactly one ether group.

In a specific embodiment, the smoothing agent is chosen from the groupcomprising propylene glycol butyl ether (available from Dow Chemicalunder the trade designation DOWANOL PnB) and ethylene glycol butyl ether(available from Dow Chemical under the trade designation ButylCELLOSOLVE), and mixtures thereof.

In addition to the components discussed above, other components may beadded to the wall repair compound. These may include, for example,water, which may be added at the end of the production process, forfinal adjustment of e.g., viscosity. Thus in certain embodiments water(in addition to the water present in the aqueous latex binder emulsion)may be added to the formulation. Other additives that may be presentinclude preservatives which may have advantageous effects on the wallrepair compound during storage, and may also serve to minimize thedegree to which mold or fungus may grow on the dried wall repaircompound. Thus in certain embodiments, the wall repair compounddisclosed herein can thus comprise at least about 0.1, 0.2 or 0.3percent by weight of a preservative or preservatives. In furtherembodiments, the wall repair compound disclosed herein comprises at mostabout 0.8 percent, 0.6 or 0.4 percent by weight of a preservative orpreservatives. Suitable preservatives include, for example, thoseavailable under the designation Mergal 192 and Polyphase P20T, from TroyCorporation of Florham Park, N.J.

The wall repair compound disclosed herein can also comprise dustreducing additives which in some circumstances may serve to furtherreduce the quantity of airborne dust particles generated when sandingthe dried, hardened wall repair compound. Exemplary additives mayinclude oils (such as mineral oils, vegetable oils, and animal oils),waxes (including natural and synthetic waxes), and the like. Suitableadditives may be chosen for example from those discussed in U.S. Pat.No. 6,358,309, herein incorporated by reference for this purpose.

Other components may also be added for various purposes, including butnot limited to, antifreeze additives, surfactants, defoamers,plasticizers (e.g., for the polymeric binder used), reinforcing fibers,and so on. Such additives may be included as long as they do not detractfrom the properties of the wall repair compound, as related above.

This application is a divisional of U.S. patent application Ser. No.14/833,962, filed 24 Aug. 2015 and now allowed, which was a divisionalof U.S. patent application Ser. No. 14/180,789, now issued as U.S. Pat.No. 9,115,267, which was a divisional of U.S. patent application Ser.No. 13/938,770, now issued as U.S. Pat. No. 8,691,889, which was adivisional of U.S. patent application Ser. No. 12/997,212, now issued asU.S. Pat. No. 8,507,587, which was a national stage filing under 35U.S.C. 371 of PCT/US2009/045778, filed Jun. 1, 2009, which claimedpriority to U.S. Provisional Application No. 61/061,274, filed Jun. 13,2008, the disclosures of all of which are incorporated by reference intheir entirety herein. It is to be understood that the followingexamples are merely illustrative and are in no way to be interpreted aslimiting the scope of the invention.

EXAMPLES Example 1

A batch of wall repair compound was synthesized by the following generalmethods. The following equipment was provided: a high shear mixerequipped with a Cowles Blade, and a low shear (Hobart) mixer. UCAR Latex626 (binder emulsion) was obtained from Dow Chemical. K-20 Glass bubbleswere obtained from 3M Company. W210 Ceramic Microspheres were obtainedfrom 3M Company. Polyphase P20T and Mergal 192 biocides were obtainedfrom Troy Corporation. Propylene glycol butyl ether (CAS Number5131-66-8) was obtained from Sigma-Aldrich, St. Louis, Mo., under theproduct number 484415 (and is believed to be substantially equivalent tothe product obtainable from Dow Chemical under the trade designationDowanol PnB). The UCAR 626 aqueous binder emulsion was added to asuitable sized beaker that was being stirred with an overhead drivenCowles mixing blade set on low speed. The P20T, 192, and propyleneglycol butyl ether were then added sequentially, while stirring on lowspeed. Following this, the W210 ceramic microspheres were slowly addedwith the mixer initially set on low speed. As the viscosity of themixture built upon addition of the ceramic microspheres, the mixer speedwas increased. After addition was complete, mixing of this pre-mix wascontinued for approximately 5 minutes. The premix was then used withoutdelay in the following step: Approximately 30 percent of the eventualtotal amount of glass bubble filler was added to the mixing bowl of thelow shear mixer. The premix was then added to the mixer by aid of arubber spatula and the mixer started on low speed. Slowly, the remainderof the glass bubbles was added to the low shear mixing bowl. Uponcompleting the addition of the glass bubbles the mixer speed wasincreased to medium for approximately one minute, then to high forapproximately two minutes. The mixer was then stopped and the batch wasinspected. The mixture was then transferred to a plastic bucket with alid, for storage.

All components listed in Table 1 for Example 1 are in weight percent, ofthe wall repair compound as formulated. (UCAR 626 is an aqueous emulsioncomprising 50 percent total solids, as discussed previously herein). Thebatch size was approximately 2 kg. It should be understood that thepercentages reported for this and the other Examples herein reflect theaccuracy and tolerances of the apparatus and measurements used.

TABLE 1 Component Weight Percent UCAR Binder Emulsion 626 57.32 K-20Glass Bubbles 25.95 Ceramic Microspheres 15.94 Propylene Glycol ButylEther 0.24 Polyphase P20T 0.42 Mergal 192 0.11

Example 2

A batch of wall repair compound was synthesized by the following generalmethods. The following equipment was provided: a high shear mixerequipped with a Cowles Blade, and a low shear (Hobart) mixer. UCAR Latex626 (binder emulsion) was obtained from Dow Chemical. K-20 Glass bubbleswere obtained from 3M Company. W210 Ceramic Microspheres were obtainedfrom 3M Company. Polyphase P20T and Mergal 192 biocides were obtainedfrom Troy Corporation. Propylene glycol butyl ether (CAS Number5131-66-8) was obtained from Sigma-Aldrich, St. Louis, Mo., under theproduct number 484415 (and is believed to be substantially equivalent tothe product obtainable from Dow Chemical under the trade designationDowanol PnB). The UCAR 626 aqueous binder emulsion was added to asuitable sized beaker that was being stirred with an overhead drivenCowles mixing blade set on low speed. The P20T, 192, and propyleneglycol butyl ether were then added sequentially, while stirring on lowspeed. Following this, the W210 ceramic microspheres were slowly addedwith the mixer initially set on low speed. As the viscosity of themixture built upon addition of the ceramic microspheres, the mixer speedwas increased. After addition was complete, mixing of this pre-mix wascontinued for approximately 5 minutes. The premix was then used withoutdelay in the following step: Approximately 30 percent of the eventualtotal amount of glass bubble filler was added to the mixing bowl of thelow shear mixer. The premix was then added to the mixer by aid of arubber spatula and the mixer started on low speed. Slowly, the remainderof the glass bubbles was added to the low shear mixing bowl. Uponcompleting the addition of the glass bubbles the mixer speed wasincreased to medium for approximately one minute, then to high forapproximately two minutes. The mixer was then stopped and the batch wasinspected. Make-up water was then added to adjust the viscosity asdesired and the mixer was operated again at high speed for a short time,until the batch appeared uniform. The mixture was then transferred to aplastic bucket with a lid, for storage.

All components listed in Table 2 for Example 2 are in weight percent, ofthe wall repair compound as formulated. (The weight percent listed forMake-up Water refers to water added as described above for viscosityadjustment, in addition to the water present in the UCAR emulsion). Thebatch size was approximately 1.8 kg.

TABLE 2 Component Weight Percent UCAR Binder Emulsion 626 55.63 K-20Glass Bubbles 25.18 Ceramic Microspheres 15.48 Propylene Glycol ButylEther 0.048 Polyphase P20T 0.41 Mergal 192 0.10 Make-up Water 3.15

Example 3

A batch of wall repair compound was synthesized by the following generalmethods. The following equipment was provided: a high shear mixerequipped with a Cowles Blade, and a low shear (Hobart) mixer. UCAR Latex626 (binder emulsion) was obtained from Dow Chemical. K-20 Glass bubbleswere obtained from 3M Company. W210 Ceramic Microspheres were obtainedfrom 3M Company. Polyphase P20T and Mergal 192 biocides were obtainedfrom Troy Corporation. Propylene glycol butyl ether (CAS Number5131-66-8) was obtained from Sigma-Aldrich, St. Louis, Mo., under theproduct number 484415 (and is believed to be substantially equivalent tothe product obtainable from Dow Chemical under the trade designationDowanol PnB). The UCAR 626 aqueous binder emulsion was added to asuitable sized beaker that was being stirred with an overhead drivenCowles mixing blade set on low speed. The P20T, 192, and propyleneglycol butyl ether were then added sequentially, while stirring on lowspeed. Following this, the W210 ceramic microspheres were slowly addedwith the mixer initially set on low speed. As the viscosity of themixture built upon addition of the ceramic microspheres, the mixer speedwas increased. After addition was complete, mixing of this pre-mix wascontinued for approximately 5 minutes. The premix was then used withoutdelay in the following step: Approximately 30 percent of the eventualtotal amount of glass bubble filler was added to the mixing bowl of thelow shear mixer. The premix was then added to the mixer by aid of arubber spatula and the mixer started on low speed. Slowly, the remainderof the glass bubbles was added to the low shear mixing bowl. Uponcompleting the addition of the glass bubbles the mixer speed wasincreased to medium for approximately one minute, then to high forapproximately two minutes. The mixer was then stopped and the batch wasinspected. Make-up water was then added to adjust the viscosity asdesired and the mixer was operated again at high speed for a short time,until the batch appeared uniform. The mixture was then transferred to aplastic bucket with a lid, for storage.

All components listed in Table 3 for Example 3 are in weight percent, ofthe wall repair compound as formulated. (The weight percent listed forMake-up Water refers to water added as described above for viscosityadjustment, in addition to the water present in the UCAR emulsion). Thebatch size was approximately 1.8 kg.

TABLE 3 Component Weight Percent UCAR Binder Emulsion 626 55.23 K-20Glass Bubbles 25.00 Ceramic Microspheres 15.37 Propylene Glycol ButylEther 2.07 Polyphase P20T 0.40 Mergal 192 0.10 Make-up Water 1.81

Example 4

A batch of wall repair compound was synthesized by the following generalmethods. The following equipment was provided: a high shear mixerequipped with a Cowles Blade, and a low shear (Hobart) mixer. UCAR Latex626 (binder emulsion) was obtained from Dow Chemical. K-20 Glass bubbleswere obtained from 3M Company. Calcium carbonate was obtained from EMDChemicals under the trade designation CX01105. Polyphase P20T and Mergal192 biocides were obtained from Troy Corporation. Propylene glycol butylether (CAS Number 5131-66-8) was obtained from Sigma-Aldrich, St. Louis,Mo., under the product number 484415 (and is believed to besubstantially equivalent to the product obtainable from Dow Chemicalunder the trade designation Dowanol PnB). The desired amount of waterwas added to a suitable sized beaker that was then stirred with anoverhead driven Cowles mixing blade set on low speed. The xanthan gumwas then slowly added. As the gum dissolved in the water the viscosityincreased and the speed of the mixer was increased. The propylene glycolbutyl ether and the Mergal 192 were then added while stirring continued.Following this, the calcium carbonate was slowly added with high speedstirring. This premix was then added below as follows.

The low shear mixer bowl was charged with the UCAR 626 and the PolyphaseP20T. The above premix was then added and the mixture stirred at lowspeed until relatively homogeneous. The K-20 glass bubbles were thenslowly added with low speed stirring continuing. After addition of theglass bubbles was complete, the mixer was operated at high speed forapproximately one minute. The mixing bowl was then lowered and the wallof the bowl was scraped with a spatula to make sure no cavities orpockets remained. The mixing bowl was then replaced in position and themixer operated for approximately one additional minute at high speed.The mixer was then stopped and the batch was inspected. The mixture wasthen transferred to a plastic bucket with a lid, for storage.

All components listed in Table 4 for Example 4 are in weight percent, ofthe wall repair compound as formulated. (The weight percent listed forWater refers to water added initially as described above, in addition tothe water present in the UCAR emulsion). The batch size wasapproximately 1 kg.

TABLE 4 Component Weight Percent UCAR Binder Emulsion 626 48.26 K-20Glass Bubbles 21.85 Calcium Carbonate 16.78 Propylene Glycol Butyl Ether0.20 Polyphase P20T 0.36 Mergal 192 0.09 Xanthan Gum 0.05 Water 12.41

Example 5

A batch of wall repair compound was synthesized by the following generalmethods. The following equipment was provided: a high shear mixerequipped with a Cowles Blade, and a low shear (Hobart) mixer. UCAR Latex626 (binder emulsion) was obtained from Dow Chemical. K-20 Glass bubbleswere obtained from 3M Company. Calcium carbonate was obtained from EMDChemicals under the trade designation CX01105. Polyphase P20T and Mergal192 biocides were obtained from Troy Corporation. Ethylene glycol butylether (CAS Number 111-76-2) was obtained from Sigma-Aldrich, St. Louis,Mo., under the product number 48, 428-8 (and is believed to besubstantially equivalent to the product obtainable from Dow Chemicalunder the trade designation Butyl CELLOSOLVE). The desired amount ofwater was added to a suitable sized beaker that was then stirred with anoverhead driven Cowles mixing blade set on low speed. The ethyleneglycol butyl ether and the Mergal 192 were then added while stirringcontinued. Following this, the calcium carbonate was slowly added withhigh speed stirring. This premix was then added below as follows.

The low shear mixer bowl was charged with the UCAR 626 and the PolyphaseP20T. The above premix was then added and the mixture stirred at lowspeed until relatively homogeneous. The K-20 glass bubbles were thenslowly added with low speed stirring continuing. After addition of theglass bubbles was complete, the mixer was operated at high speed forapproximately one minute. The mixing bowl was then lowered and the wallof the bowl were scraped with a spatula to make sure no cavities orpockets remained. The mixing bowl was then replaced in position and themixer operated for approximately one additional minute at high speed.The mixer was then stopped and the batch was inspected. The mixture wasthen transferred to a plastic bucket with a lid, for storage.

All components listed in Table 5 for Example 5 are in weight percent, ofthe wall repair compound as formulated. (The weight percent listed forWater refers to water added initially as described above, in addition tothe water present in the UCAR emulsion). The batch size wasapproximately 0.3 kg.

TABLE 5 Component Weight Percent UCAR Binder Emulsion 626 48.28 K-20Glass Bubbles 21.86 Calcium Carbonate 16.79 Ethylene Glycol Butyl Ether0.21 Polyphase P20T 0.36 Mergal 192 0.09 Water 12.42

Samples made according to the compositions and procedures of Examples,1, 2, 3, 4 and 5 were found by the inventors to exhibit advantageouslysmooth consistency; easy spreadability; and, resistance to sagging,running or slumping when applied to a vertical wall.

Shrink Measurement

Because the wall repair compounds described herein typically comprised adensity (specific gravity) less than that of water and of common oilsand liquids, the compounds were not easily characterizable byconventional shrink measurements that rely on measuring an amount ofliquid displaced. Accordingly, a simple, semi-quantitative method ofascertaining shrinkage was developed. A lid (from a 1 gallon glass jar)measuring approximately 3.5 inches in diameter and approximately 0.4inches deep was completely filled with a sample of wall repair compound.The exposed (top) surface of the sample was leveled even with the upperedge of the lid by running a wide putty knife over the surface of thesample. The sample was then allowed to dry for three days under ambient(room) conditions.

After the completion of the three days drying, the sample was inspectedfor any cracking. The sample was also inspected for shrinkage (whichwould be manifested as a depression of the exposed surface of the driedwall repair compound below the upper edge of the lid). Any suchdepression could be measured and used in combination with the volume ofmaterial in the sample, to obtain a semi-quantitative estimate of theshrinkage that occurred in drying.

For samples made according to the compositions and procedures ofExamples, 1, 2, 3, 4 and 5, no cracking was observed. For these samples,any depression of the exposed surface relative to the lid rim edgeappeared to be at or below an amount observable to the eye. The minimumamount of such depression which would be observable to the eye beingestimated by the inventors as being a few thousandths of an inch, it wasthus conservatively estimated that these samples exhibited a shrinkageupon drying of less than about 2.5 percent (e.g., 0.010 inch (tenthousandths of an inch) divided by 0.4 inch).

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the invention. Within the guidelinespresented herein, it is possible to vary the composition of the wallrepair compounds as desired for particular purposes. For example, theinventors have found that increasing the amount of glass bubbles in theformulation relative to the amount of ceramic microspheres, may producea dried compound that is easier to sand. In further example, theinventors have found that increasing the amount of ceramic microspheresin the formulation relative to the amount of glass bubbles, may producea dried compound of higher hardness. In making such adjustments, or ingeneral, the viscosity of the compound may be varied as desired by wayof increasing or decreasing the amount of aqueous binder latex and/orthe amount of added water. All such variations and combinations arecontemplated by the inventor as being within the bounds of the conceivedinvention. Accordingly, all such embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. A wall repair compound, comprising, an aqueouslatex binder emulsion comprising an acrylic binder comprising vinylacrylic polymers or copolymers made from the polymerization of monomersthat comprise acrylate and/or methacrylate groups, wherein the aqueouslatex binder emulsion makes up at least about 40 percent by weight ofthe wall repair compound; an inorganic filler system comprising at least99% by weight glass bubbles, wherein the inorganic filler system makesup at most 50 percent by weight of the wall repair compound.
 2. Thecompound of claim 1 wherein the acrylic binder comprises a glasstransition temperature from about 15° C. to about 35° C.
 3. The compoundof claim 1 wherein the acrylic binder exhibits a glass transitiontemperature peak covering an interval of at least 5° C.
 4. The compoundof claim 1 wherein the acrylic binder comprises a glass transitiontemperature from about 15° C. to about 35° C. and exhibits a glasstransition temperature peak covering an interval of at least 5° C. 5.The compound of claim 1 wherein the inorganic filler system comprisesessentially 100% by weight glass bubbles.
 6. The compound of claim 1wherein the compound comprises one or more glycol ether smoothing agentsin an amount of at most about 2.5 percent by weight.
 7. The compound ofclaim 1 wherein the compound comprises less than about 0.1 percent byweight of inorganic thickening filler clay.
 8. The compound of claim 1wherein the aqueous latex binder emulsion comprises from about 40percent by weight to about 80 percent by weight of the compound.
 9. Thecompound of claim 1 further comprising from about 0.1 percent to about0.8 percent by weight of preservative.
 10. The compound of claim 1further comprising one or more dust reducing additives chosen from thegroup consisting of oils, waxes and mixtures thereof.
 11. The compoundof claim 1 with the proviso that the compound does not include any dustreducing additives chosen from the group consisting of oils, waxes andmixtures thereof.
 12. The compound of claim 1 wherein the compoundexhibits a shrinkage upon drying of less than about 2.5%.
 13. Thecompound of claim 1 wherein the glass bubbles exhibit a median particlesize of at least about 15 microns and at most about 80 microns.
 14. Thecompound of claim 1 wherein the glass bubbles exhibit a median particlesize of at least about 40 microns and at most about 80 microns.
 15. Thecompound of claim 1 wherein the aqueous latex binder emulsion consistsof the acrylic binder comprising vinyl acrylic polymers or copolymersmade from the polymerization of monomers that comprise acrylate and/ormethacrylate groups.
 16. A method of repairing a wall, the methodcomprising the steps of: filling a cavity in a wall with the wall repaircompound of claim 1; and, allowing the wall repair compound to dry. 17.The method of claim 16 further comprising the step of painting at leastthe dried wall repair compound.